Hydraulic motor drive



Oct. 21, 1969 v 5, F M EI'AL 3,473,442

HYDRAULIC VICTOR-DRIVE Filed Nov. 5. 1967 Sfanleg E. Farmer Thomas E.Dixon INVENTORS United States Patent 3,473,442 HYDRAULIC MOTOR DRIVEStanley E. Farmer, Gresham, and Thomas E. Dixon,

Lake Grove, Qreg, assignors to Cascade Corporation, Portland, Greg, acorporation of Oregon Filed Nov. 3, 1967, Ser. No. 680,431 int. Ci.F161: 11/02, 13/06; F16d 33/02 US. Cl. 91-412 Claims AESTRACT OF THEDISCLOSURE In a lift truck attachment having a rotatable load support, abidirectional motor drive to be operated from a source of pressure fluidfor rotating the support, such drive including a shaft geared to thesupport, a pair of reversible hydraulic motors drivingly connected tothe shaft, and a device responsive to the pressure of fluid supplied toone of the motors to control fluid flow through both motors. The deviceincludes a valve which, with a low pressure condition existing in fluidsupplied the one motor, occupies one state where it short-circuits theother motor with substantially all fluid flow from the source then beingthrough the one motor, and which occupies another state on a higherpressure condition existing in fluid supplied the one motor where itconnects the two motors in parallel, with fluid from the source dividingbetween the motors.

This invention relates to a fluid-operated motor drive. A specificembodiment of the invention includes the motor drive as a means forturning a rotatable load supporting means. Thus, the invention isdescribed herein in connection with a lift truck attachment including arotator and a pair of load clamps (load supporting means) mounted on therotator, where the motor drive is used to turn the rotator.

The rate at which fluid under pressure may be delivered by a source orpump in an organization such as a lift truck is limited. Accordingly, ithas been found desirable to provide as the fluid-operated motor drive,for rotating the rotator, means capable of turning the rotator at a lowspeed while delivering high torque, and at a substantially higher speedwhile delivering lower torque. Such produces flexibility in operation,permitting the rapid handling of light loads without sacrificing theability to handle much heavier loads. For handling ease it is importantthat the drive means adjust itself automatically to the type of loadbeing handled, to give the performance best suited for the load.Further, where the type of performance iven by a drive means isvariable, it is important that the drive means not vacillate in the typeof performance it gives, and that any transition between one type ofperformance and another by done smoothly.

Thus, a general object of the present invention is to provide a novelhydraulic motor drive which takes the above-indicated considerationsinto account in a practical and satisfactory manner.

More particularly, an object is to provide a motor drive of the typeindicated, which is capable of both highspeed, low-torque performanceand low-speed, hightorque performance, with the type of performancedetermined automatically by the amount of loading occuring in a driveshaft in the drive.

According to the invention, the drive shaft is drivingly connected to apair of hydraulic motors, and a novel pressure-sensitive device isprovided which responds to the pressure of fluid supplied to one of themotors to control fliud flow through both motors. Through suchregulation of the fluid flowing in the motors, the device 3,473,442Patented Oct. 21, 1969 controls the torque and speed operatingcharacteristics of the drive.

More specifically, with fluid supplied to the one motor at a relativelylow pressure (indicating that the load on the drive shaft is relativelylight), the pressure-sensitive device short-circuits the other motor,and pressure fluid from the source is circulated entirely through theone motor. The motor drive then operates at relatively high speed andlow torque. When the pressure of fiuid supplied the one motor becomesrelatively high (indicating that the load on the drive shaft isrelatively heavy), the device removes the short circuit from the othermotor, and connects the two motors in parallel, with pressure fluid fromthe source then flowing to both motors. The motor drive then runs at alower speed and produces greater torque.

A further object of the invention is to provide, for a motor drive ofthe type contemplated, a novel changeover valve controlling the type ofperformance obtained from the motor drive through controlling whetherone or two motors in the drive are operating. The changeover valve isresponsive to fluid pressure supplied one motor, and is constructed sothat a greater pressure of fluid is required in the conduit systemsupplying the one motor to change the operation from one where one motoroperates alone, to one where both motors operate together, than isrequired to maintain the two motors in a state where both are operatingtogether. With this feature of the invention, tendencies of the motordrive to alternate back and forth between operation where one motoroperates alone and operation where both motors operate conjointly isinhibited.

Yet another object is to provide a motor drive as outlined which isadapted for bidirectional operation.

These and other objects and advantages attained by the invention, willbecome more fully apparent as the description which follows is read inconjunction with the accompanying drawings, wherein:

FIG. 1 is a simplified side elevation illustrating loadhandlingapparatus adapted for mounting on an industrial lift truck, with suchapparatus including a rotator supporting a pair of load clamps, andemploying a motor drive constructed according to the invention tooperate the rotator;

FIG. 2 is a schematic diagram, partly in block form, furtherillustrating the motor drive of FIG. 1 (with the drive removed from therotator in FIG. 1), and illustrating connections between the drive and asource of pressure fluid; and

FIG. 3 is an enlarged view illustrating details of a pressure-sensitivedevice employed in the motor drive of FIGS. 1 and '2.

Turning now to the drawings and referring first to FIG. 1, indicatedgenerally at 10 is load-handling apparatus, including a rotator 12 and aload-clamping mechanism, or load support, 14 adapted to be mounted onthe front of an industrial lift truck. The rotator includes an uprightflat base plate 16 which may be mounted on the usual elevatable carriage(not shown) in a lift truck through a mounting plate 18 (suitablyfastened to the carriage) and brackets 20, 22 secured to the back ofplate 16. The rotator further includes an upright, rotatable face plate24- disposed in front of and substantially parallel with plate 16. Plate24 is rotatably mounted on plate 16 through a conventional bearingassembly including an outer race partially shown at 26a fastened to thefront of plate 16, and a relatively rotatable inner race, partiallyshown at 26b, secured to the back of plate 24. The axis of rotation ofplate 24, shown at 28, extends in a direction normal to the planes ofplates 16, 24.

Clamping mechanism 14 includes a pair of opposed, relatively movable,power-operated clamping arms 30, 32 having clamping pads 30a, 32a,respectively, mounted on their forward extremities. The arms are mountedfor movement toward and away from one another on a frame 34, and throughthis frame the mechanism is suitably anchored to the front of plate 24in the rotator. With movement of the arms toward one another, theclamping pads are adapted to clamp against opposite sides of acylindrical load, such as a paper roll. For a more detailed descriptionof a load clamping mechanism similar to that shown herein reference ismade to a copending application of Donald M. Faust and Henry F.Chochrek, entitled Clamping Mechanism, filed June 9, 1967, Ser. No.645,027.

Plate 24 in the rotator is rotated under power by means of a hydraulicmotor drive generally indicated at 36 (see FIGS. 1 and 2). The motordrive includes a pair of conventional reversible hydraulic motors 38, 40with their casings suitably mounted on the casing of a drive unit 42,the latter being anchored to the back of plate 1'6. Motors 38, 40 aresimilar in construction, and include corresponding ports 38a, 38b and40a, 4012 (represented in block form), respectively, which accommodatethe flow of pressure fluid through the motors. With pressure fluidintroduced into ports 38a, 40a (or into ports 38b, 40b), the motorsoperate in the same direction. The motors are drivingly connected toopposite ends of a drive shaft 44 which extends between the motors, andthrough the housing in unit 42.

Shaft 44 is connected to a worm screw 46 in unit 42 which drives a wormgear 48 in the unit. A driving connection is established between gear 48and plate 24 in the rotator by means of a shaft 50 which is turned bythe gear, and suitable gears (not shown) connecting the shaft to theplate.

Further describing motor drive 36, and referring to FIG. 2, the motordrive includes a pressure-sensitive device (shown in block form at 52)having ports 52a, 52b, 52c, 52d. Constructional details of device 52will be considered more fully in a later discussion. Device 52 isconnected to motor 38 through pair of conduits 54, 56, and to motor 40through pairs of conduits 58, 60 and 62, 64. More specifically, conduits54, 56 have one set of ends connected to ports 38a, 38b, respectively,and an opposite set of ends connected to ports 52a, 52b, respectively.Conduits 58, 60 have one set of ends connected to ports 52c, 52d,respectively, and an opposite set of ends connected to conduits 62, 64respectively. Conduits 62, 64, in turn, have one set of ends connectedto motor ports 40a, 40b, respectively.

Hydraulic fluid under pressure for operating motors 38, 40 is furnishedfrom a source generally indicated at '66 including a reservoir 68, apump 70, a pressure relief valve 72, and a main control valve 74. Thesemay be conventional pieces of equipment found on the usual lift truck.Pump 70 is connected to the reservoir by a conduit 76 and to valve 74 bya conduit 78. Valve 74 is connected directly to the reservoir by aconduit 80. Pressure relief valve 72 is connected to conduit 78 by aconduit 82, and to conduit 80' by a conduit 84. Valve 74 is connected asshown to the other set of ends of previously-mentioned conduits 62, 64.

In FIG. 2, the valve spool of valve 74 is illustrated as a rectangledivided into three squares, with each square containing symbolsillustrating how fluid flow takes place through the valve for variouspositions of the spool. The spool is normally biased to the neutralposition in which it is shown by means of springs 86, 88 acting on itsopposite ends, and the spool may be adjusted to different positionsthrough the operation of manual adjustment means 90, 92. With the valvespool in its neutral position, conduits 62, 64 are closed off where theyare connected to the valve, and conduits 78, 80 communicate with oneanother through the valve. With the valve spool shifted downwardly fromits neutral position in FIG. 2, pressure fluid is admitted to conduit 62and exhausted from conduit 64. On the other hand, with the spool shiftedupwardly from its neutral position in FIG. 2. pressure fluid is admittedto conduit 64 and exhausted from conduit 62.

Turning now to FIG. 3, and describing in detail the construction ofpressure-sensitive device 52, the device includes a body 94. Extendingcompletely through the body, from one side to the other in FIG. 3, is anelongated cylindrical passage including a central section 96 having onediameter, and a pair of end sections 98, which are similar to oneanother and which have somewhat larger diameters than the centralsection. Where section 98 joins with section 96 there is an annularshoulder 98a facing to the left in FIG. 3. A similar shoulder 100aexists, facing to the right in the figure. where section 100 joinssection 96. The outer ends of passage section 98, 100 are closed off byplugs 102, 104, respectively, which are screwed into the sections.

Communicating with passage section 96 at points spaced along its length,and on diametrically opposite sides of the section, are pairs of bores106, 108 and 110. 112 which icommunicate with previously-mentioned ports52a, 52b, and 52c, 52d, respectively. Bores 106, 108 are somewhat moreclosely spaced together than are bores 110, 112.

Extending into body 94 from the lower side thereof in FIG. 3, andcommunicating with passage sections 98, 100, are pairs of axiallyaligned bores 114, 116, and 118, 120, respectively. Bores 114, 118, havesomewhat larger inside diameters than do bores 116, 120. The lower endsof bores 114, 118 are closed oif by plugs 122, 124, respectively. Theupper ends of bores 114, 118 communicate through passages 126, 128 withbores 110, 112, respectively.

Extending into the left and right sides of body 94 in FIG. 3, andintersecting bores 116, at substantially right angles, are bores 130,132, respectively. The outer ends of bores 130, 132 are closed off byplugs 134, 136. respectively, and the inner ends of the borescommunicate with bores 110, 112 through bores 138, respectively. Thecross-sectional areas of bores 138, 140 are substantially the same, andare considerably smaller than those of bores 130, 132.

Slidably mounted in passage section 96 is an elongated valve spool ormember 142 having a length substantially the same as that of passagesection 96. Extending about the outside of the spool, substantiallymidway between its opposite ends is an annular channel 144. Extendingaxially and inwardly from the right end of the spool in FIG. 3 is anelongated cylindrical passage 146. The left end of passage 146communicates with a passage 148 (having a substantially smaller insidediameter than that of passage 146) and this passage in turn opens ontothe left end of the spool in FIG. 3.

The spool is illustrated in a centered position relative to the oppositeends of passage section 96, and in this position it closes off the upperends of bores 110, 112 while permitting the lower ends of bores 106, 108to communicate with one another through channel 144, The spool is urgedto this position by means of pilots 150, 152 slidably received inpassage sections 98, 100, respectively, and a pair of similar springs154, 156 which act between plugs 102, 104 and pilots 150, 152,respectively. The pilots are similar in construction, and consideringpilot 150, it includes an elongated cylindrical part a having an axiallyextending passage 15012. The pilot further includes an annular flange150a projecting radially outwardly from part 150a. In FIG. 3, the flangein pilot 150 seats against shoulder 98a, and against the left end ofspool 142; The flange in pilot 152, similarly, seats against shoulder100a and the right end of the spool.

According to the invention, with shifting of the spool to the right inFIG. 3, the connection between bores 106.

108 is broken, bore 110 communicates directly through passage section 96with bore 106, and bore 112 communicates through channel 144 with bore108. Similarly, with shifting of the spool to the left, the connectionbetween bores 106, 108 is broken, and these bores communicate with bores110, 112, respectively.

Blocking communication between bores 114, 116 is a ball 158. The ball isbiased to the position shown, seated against the shoulder existing wherebores 114, 116 join, by means of a spring 160 acting between the balland plug 122. A similar ball and spring 162, 164, respectively, areprovided in bore 118 blocking communication between bores 118, 120.Normally closing off bore 138 where it joins with bore 130 is a ball166. Ball 166 is biased to the position shown by a spring 168 which actsbetween the ball and plug 134. In a similar fashion, a ball 170 biasedby a spring 172 acting between the ball and plug 136 blockscommunication between bores 132, 140. Springs 168, 172 are substantiallythe same in construction.

Considering briefly the operation of device 52, spool 142 and theassociated parts controlled by the spool constitute a change-over valvein the device. With pressure fluid supplied to conduit 58, such fluid isintroduced through port 520 into bores 110, 138, where it acts upon ball166. So long as the pressure of this fluid remains below a certainpressure, the ball remains in the position shown in FIG. 3. Spool 142will remain centered in passage section 96, with the upper ends of bores110, 112 closed olf, and the lower ends of bores 106, 108 communicatingwith one another through channel 144.

Some leakage of fluid may occur around the left end of the valve spool,and any fluid which leaks from bore 110 to the region adjacent the leftend of the spool flows through passages 148, 146 to passage section 100and bore 120. When the pressure of fluid in bore 120 is suflicient toshift ball 162 downwardly against spring 164, such fluid exhausts toconduit 60 through passage 128 and bore 112.

Upon the fluid pressure in bores 110, 138 exceeding a certain pressure,ball 166 shifts to open the left end of bore 138, and fluid flowsthrough bores 130, 116, passage section 98 and passage 1501) to the leftend of spool 142. The spool shifts to the right in FIG. 3 against pilot152 and spring 156. Thereupon bore 110 communicates with bore 106, andbore 112 communicates with bore 108. The direct connection between thelower ends of bores 106, 108 is broken. In addition, the left end of thespool (referred to as a piston face region) moves to a position where itis directly exposed to fluid in bore 110.

Upon shifting of the spool to the right as just explained, fluidcontained in passage 146, passage section 100, and bore 120 acts uponball 162 to lower it in bore 118, whereupon such fluid exhausts throughpassage 128 and bore 112. Thereafter, and with the spool continuing tooccupy a position shifted to the right, a relatively small amount offluid acting on the left end of the spool leaks through passages 148,146 and is exhausted in the same manner.

With the spool 142 shifted to the right in the control device and theleft end of the spool exposed to the fluid under pressure in bore 110, asubstantial surface area in the spool is acted upon by such pressurefluid to produce a substantial force tending to hold the spool in itsrightof-center position. Spring 156 resisting such movement and spring168 resisting movement of ball 166 to open bore 138 are selected so thata substantially greater pressure of fluid is required in bore 110 toopen bore 138 and initiate travel of the spool than is required tomaintain the spool in its right-of-center position. Ball 166 thereforefunctions as and is referred to herein as a starter valve means locatedin a passage extending from bore 110 and communicating with the left endof the valve spool (or a piston face region in the spool) with this leftend nonexposed directly to fluid under pressure in bore 110.

With motor 38 and motor 40 connected in parallel, and being suppliedfrom the source, as occurs with such shifting of the valve spool, asubstantial drop in pressure is required in conduit 58 before th controldevice will operate to remove motor 38 from the source. This is becausea lower pressure is required to maintain the valve spool in its adjustedposition than is required initially to start movement of the valve spoolfrom its neutral position. Accordingly vacillation in the operation ofthe drive is minimized.

A similar operation takes place in device 52 with pressure fluidfurnished to conduit 60 rather than to conduit 58. In this case, uponthe pressure of fluid in bores 112, 14-0 exceeding a certain level,spool 142 shifts from its neutral or centered position to the left inFIG, 3. As in the first case described above, such shifting of the spoolresults in a breaking of the direct connection between bores 106, 108,and in connecting bores 110, 106 and bores 112, 108.

Explaining now how the motor drive operates, valve 74 may be adjusted toadmit pressure fluid to conduits 62, 58 (with fluid permitted to exhaustfrom conduits 64, 60) to produce operation of the motor drive in onedirection. Assuming that the load demand exerted on shaft 44 (resultingfrom the action of a load held between the clamping pads) is relativelylight, the pressure of fluid in conduits 62, 58 (and hence the pressureof fluid acting on ball 166 in device 52), will be relatively low. Spool142 remains in its neutral position blocking bores 110, 112 and thusstopping circulation of fluid between source 66 and motor 38. Allpressure fluid coming from the source as a consequence circulatesthrough motor 40, and motor 40 operates to drive shaft 44 at relativelyhigh speed.

With turning of shaft 44, and because the shaft is common to bothmotors, motor 38 operates as a pump, and circulates fluid in conduits54, 56 which have been short-circuited by the valve spool. It will benoted that the body of fluid circulating in the closed system producedby such short circuit is isolated from the pump and reservoir.

Should the load demand on shaft 44 increase, this results in an increasein the pressure of fluid in conduits 62, 58. Upon the pressure of suchfluid exceeding a certain level, ball 166 in device 52 shifts to admitpressure fluid against the left end of spool 142 in FIG. 3. The spoolthen shifts to the right to remove the short circuit across motor 38,and to connect conduits 54, 58 and conduits 56, 60. When this occurs,pressure fluid in conduit 58 flows through the device to motor 38, andfluid exhausts from the motor through the device to conduit 60.Accordingly, fluid flowing from source 66 divides between motors 38, 40with the motors together driving shaft 44. The drive then delivershigher torque at a slower speed.

To reverse the rotational direction of the motors, valve 74 is adjustedto admit pressure fluid to conduits 64, 60. With such an adjustmentmade, the operation of motor drive 36 is similar to the operation justdescribed. In this case, however, it is the pressure of fluid inconduits 64, 60 which determines whether one or both of the motorsdrives shaft 44-.

Thus, the invention provides a novel hydraulic motor drive for driving arotating shaft, where power is transmitted to the shaft at a torque andwith a rotational speed which depends upon the loading of the shaft. Thedrive employes a pair of motors with one of such motors beingshort-circuited to produce high-speed, lowtorque characteristics.

While an embodiment of the invention has been described herein, it isappreciated that variations and modifications may be made withoutdeparting from the spirit of the invention. Accordingly, it is desiredto cover all such variations and modifications which would be apparentto those skilled in the art, and that come within the scope of theappended claims.

It is claimed and desired to secure by Letters Patent:

1. A motor drive to be operated from a source of fluid under pressurecomprising a shaft and a pair of hydraulic motors drivingly connected tothe shaft,

a conduit system interconnecting said source and said motors forcirculating fluid between each of said motors and said source, andincluding a pair of conduits for each motor for supplying fluid to andexhausting it from the motor,

said conduit system further comprising a pressure sensitive deviceincluding fluid-pressure-operated valve means interposed between saidpair of conduits for one motor responsive to the pressure of fluidsupplied to the other motor operable, with a low pressure conditionexisting in fluid supplied said other motor, to establish a shortcircuit between the pair of conduits for said one motor producing anisolated body of fluid for circulation through said one motor, saidvalve means with a higher pressure condition existing in fluid suppliedsaid other motor operating automatically to remove said short circuitand to connect said one motor through the pair of conduits providedtherefor to said source for the circulation of fluid between the sourceand the one motor.

2. The motor drive of claim 1, wherein said valve means includes ashiftable valve member biased to a position establishing said shortcircuit, and held against such biasing, and with the fluid supplied saidother motor at a pre-established pressure, in another positionconnecting said one motor through the pair of conduits provided thereforto said source for the circulation of fluid between the source and theone motor.

3. The motor drive of claim 2, wherein said valve means is constructedso that with its valve member in its firstmentioned position a pressureof fluid supplied said other motor exceeding said pre-establishedpressure is required to shift the valve member to its said otherposition.

4. The motor drive of claim 3, wherein the valve member includes apiston face region which communicates with pressure fluid circulatingbetween the source of said other motor with the valve member in its saidother position thus to be acted upon by such fluid, said face regionoccupying a noncommunicating position with respect to such pressurefluid with the valve member in its said first-mentioned position.

5. The motor drive of claim 4 which further includes a fluid passagecommunicating with said face region of said valve member with said valvemember in its first-mentioned position and connected also to the pair ofconduits for said other motor to reflect the pressure of fluid suppliedto the other motor, and starter valve means is provided for said passageinhibiting flow through the passage of fluid circulated in said pair ofconduits for said other motor until the pressure of fluid supplied tothe other motor exceeds said pre-established pressure.

6. The motor drive of claim 2, wherein said motors are bidirectional,and said valve member is shiftable from its first-mentioned position totwo other positions, one of said other positions connecting said onemotor through the pair of conduits provided therefor to said source forthe circulation of fluid producing rotation of the one motor in onedirection, and the other of said other positions connecting the onemotor to said source for the circulation of fluid producing rotation ofthe one motor in the reverse direction.

7. In a lift truck attachment including a rotatable load support, abidirectional motor drive to be operated from a source of fluid underpressure for rotating the support comprising a shaft and a pair ofnected to the shaft,

a conduit system interconnecting said source and said motors forcirculating fluid between each of said motors and said source, andincluding a pair of conduits for each motor for supplying fluid to andexhausting hydraulic motors drivingly conit from the motor,

said conduit system further comprising a pressure-sensitive deviceincluding fluid-pressure-operated valve means interposed between saidpair of conduits for one motor responsive to the pressure of fluidsupplied to the other motor,

said valve means being operable, with a low pressure condition existingin fluid supplied the other motor, to short-circuit the pair of conduitsfor said one motor to produce an isolated body of fluid for circulationthrough said one motor,

said valve means being further operable automatically,

with a higher pressure condition existing in fluid supplied said othermotor, to remove said short circut, and to connect said one motorthrough the pair of conduits provided therefor to said source for thecirculation of fluid between the source and the one motor.

8. A motor drive to be operated from a source of fluid under pressurecomprising a shaft and a pair of hydraulic motors drivingly connected tothe shaft,

a conduit system interconnecting said motors and said source forcirculating fluid between the source and the motors, and including apair of conduits for each motor for supplying fluid to and exhausting itfrom the motor,

said conduit system further comprising a pressure-sensitive deviceincluding fluid-pressure-operated valve means interposed between saidpair of conduits for one motor, and responsive to the pressure of fluidsupplied the other motor for alternatively connecting and disconnectingthe one motor and said source depending on the level of such pressure,

said valve means, with the one motor and source disconnected, connectingthe same for the circulation of fluid therebetween on the pressure offluid supplied to said other motor exceeding one pressure, and with theone motor and source connected, disconnecting the same on the pressureof fluid supplied to said other motor dropping below another pressurewhich is lower than said one pressure.

9. The motor drive of claim 8, wherein said valve means includes amovable valve member which occupies one position with said source andsaid one motor disconnected and another position with said source andsaid one motor connected, said valve member including a piston faceregion which communicates with pressure fluid circulating between thesource and the other motor with the valve member in its said otherposition thus to be acted upon by such fluid, said face region occupyinga noncommunicating position with respect to such pressure fluid with thevalve member in its said one position.

10. The motor drive of claim 9 which further includes a fluid passagecommunicating with said piston face region of said valve member withsaid valve member in its said one position and connected also to thepair of conduits for said other motor to reflect the pressure of fluidsupplied the other motor, and starter valve means is provided for saidpassage inhibiting flow through the passage of fluid circulated in saidpair of conduits for said other motor until the pressure of fluidsupplied the other motor exceeds said one pressure.

References Cited UNITED STATES PATENTS 2,370,526 2/1945 Doran. 2,374,5884/1945 Doran. 2,500,627 3/1950 Chinn 6053 2,616,259 11/1952 Quintilian60-53 EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R.

